Household cleaning composition



PII 4 1950 E. w. PARKER 2,502,881

HOUSEHOLD CLEANING COMPOSITION Filed 0013. 17, 1945 Patented Apr. 4,1950 UNITED STATES PATENT OFFICE HOUSEHOLD CLEANING COMPOSITIONElizabeth Weston Parker, Washington, D. C.

Application October 17, 1945, Serial No. 622,820

Claims. l This invention relates to household cleaning compositions; andit comprises alkaline cleaners of the type used in the household forcleaning Windows, painted Work, iioors, tiling, wood-work,

-` glassware and the like; said cleaner being a nely divided mixture ofalkaline detergent salts, such as hydrated sodium metasilicate, ammoniumphosphate, sodium pyrophosphate, diand tri-- sodium phosphate, sodiumborate, sodium carbonate and the like, and having incorporated therein asmall quantity of at least one pl-I indicator having the characteristicproperty of changing color Within a pH range of about 7.5 to 9.7 to givea warning dominant color at least at the higher pH values; said mixturealso advantageously including a soap powder and/or a wetting agent; allas more fully hereinafter set forth and as claimed.

Household cleaners of the type used in general cleaning Work about thehouse are in widespread use. These cleaners contain at least onebuffering inorganic detergent salt and may contain in addition soapand/or wetting agents or the like. When added to a soft Water incleaning concentrations, which usually range from about 1A, to 3teaspoonsful (i to 1/2 ounce) to the quart or about 0.15 to 2 per centby weight, they produce a pH above 8.3. The pH produced at theseconcentrations should not substantially exceed 10.5 and preferably not9.5, in order that the cleaning solutions thus formed can be appliedwith the hands without damage either to the work or to the hands. Themaximum pH produced at concentrations of 5-10 per cent of cleaner shouldnot be above about 11. In other words these cleaners are slightly morecaustic than pure soaps but less caustic than industrial cleaners, thepH of Whose solutions frequently exceed 12. This latter type of cleanercannot be applied by hand.

While household cleaning compositions are usually fairly well buffered,so that their pH changes only slowly With concentration, it is generallytrue that, if used in concentrations much above the minimum recommended,these cleaners are likely to be deleterious or irritating to the skin.For economy reasons, as Well as for best results, it is also desirablethat these compositions be used in solutions close to the minimumrequired for production of the desired cleaning effect.

The packages in which these cleaners are sold invariably give directionsto prepare the desired cleaning solutions .by adding so manyteaspoonfuls or so many ounces oi the cleaner to a quart or a gallon ofWater or the like. Directions of this type, of course, leave much to bedesired. The persons using these cleaners must of necessity employordinary tap Water in making the cleaning solutions and tap Waters varywidely in hardness. Directions which would be suitable for the Water inone city might be quite unsuitable lor the Water in a neighboring city.

Attempts have been made to overcome the above difculties by the use ofsimple dyes added to cleaning compositions. The dyes used in this mannerdid not change in color upon change in pH but an attempt was made to addthem in such quantities that, when the proper amount of composition wasadded to the Water, a deiinite fluorescent or colored'effect wasproduced. It is obvious, of course, that the color produced by such amethod depends only upon the amount of dye added to the Water,regardless of the hardness of the latter. If the dye is evenly dispersedthrough the cleaner, the color of the cleaning solution increasesdirectly as its concentration increases. There is no sharp change incolor and there is no way of judging by the inexperienced what depth ofcolor is correct or how Soft a water is produced. The dye, therefore,serves no useful purpose until the user of the composition has hadconsiderable experience in making up cleaning solutions from a singletap water.

My invention is applicable to cleaning compositions of widely dilerentcharacter. Any of the usual alkaline detergent salts can be employed inthese compositions, including sodium silicates, sodium phosphates,sodium car-bonates, ammonium salts, sodium borates, salts of quaternaryammonium bases, the so-called cationic soaps and the like. It is onlynecessary that the composition be one which when added to Water producesa change in pH over a range which extends throughout and somewhat beyondits optimum concentration range. The pH indicator for a given cleaningcomposition must be selected, of course, in such manner as to produce acharacteristic color at at least some point Within the optimumconcentration range of the cleaner.

I have found that When a critical quantity of certain pI-I indicatorsare admixed with dry household detergent compositions and when these drymixtures are added to water gradually, a color change Will becomenoticeable when optimum cleaning concentrations are reached, such as onespoonful to the quart, for example, and that when more cleaner is addedthe color changes rapidly in intensity, not directly with the quantityadded, as in the case of an ordinary dye, but more nearly as the squareof the quantity added. The

low a pH of 9.7.

reason for this is that the color change is due not only to theincreased concentration of the dye in the water but also to the pH ofthe solution. The total color change due to these faotors can be madevery marked by suitable choice of indicator and detergent composition.Owing to the rapidity of color change produced in this fashion, aperson, told to add cleaner to water until a faint color is produced,might stop when he had added an excess amounting to say 25 to 50 percent but wouldrarely exceed the latter figure, especially if thedirections should state that additional water should be added if adistinct color should develop. This new process therefore provides amethod of preparing cleaning solutions which takes into. account thehardness of the water.

When the pH of the water rises, 'due to addition of cleaner, to about8.2 this provcsthat the bicarbonate or temporary hardness of the waterhas been neutralized by the alkali of the cleaner. Usually a slightexcess of` cleaner above this point produces satisfactory cleaningwithout beingk irritating to the hands.

A cleaner which does not produce an eiective .cleaning solution at a pHbelow about 9.7 cannot be classed as a `household cleaner. It followsthat a suitable pH indicatoivfor the purposes of this inventionmust havea color range the lower end of which extends at leastsome distance be-And, as will beshown later,.for best results, the lower end of the rangeof the indicators dominant Vcolor should not lie below a pH of about7.2.to 8.0.

I have found surprisingly that for best results the pI-I indicator`shouldbe chosen in such :fashion that it produces a change in color asclose as possible to the pI-I at which the cleaning cornposition `firstbecomes effective. In other words for best results the end point of theindicator should occur at a pH substantially coinciding with that of thelower end of the veffective cleaning range of the detergent. Thus, ifthe composition rstmakes an eiective cleaning solution upon the additionoabout arteaspoonful `to a quart of soft water andif a pH of about-8.7is produced at thisconcentration, for best results an indicatorshouldibe chosen .whose colorrange starts, i. e. whose end pointflieseter-just below apI-I of 8.7, say from about 8.3 to 8.7. .If the endpoint lies below about 7.5,the color change produced per unit ofcleaneradded in-the eiective cleaning range will be noticeably inferiorand will approximate that produced by a simple dye.

The explanation for theserunexpected results is believed to lie in theaccompanying drawing which shows curves of color .intensity for twodifferent indicators as a function of the amount of detergent added towater-to produce a cleaning solution.

In this figure a curve (marked pI-I Curve) is given which shows the pHvalues of the solution as the cleaning composition is added thereto. Thecleaner illustrated is a typical household cleaner having an optimumcleaning range of from 0.5 to 0.75 per cent dry weight giving a pHranging from about V8.7 to 9.2. The concentrations are plotted asabscissas with the pHvalues as ordinates, the numerical values ofthepI-I being givenalong the axis at the left of t-e figure. This curvesstarts at apHlof 7 with zero concentration of detergent. ThepI-I-increases rapidly with small increases of `concentration at thestart of the curve but the rate of increase rapidly falls o until, -at aconcentration of about 2.5

4 per cent detergent the curve rises above a pH of 10 but becomes almostparallel with the concentration axis due to the buering eiect of thedetergent salts.

A line representing the color intensity of a simple dye in the solutionis also given. rIhis is, of course, a straight line since the dye isevenly dispersed throughout the cleaner and its color intensity in thesolution increases directly with the concentration of the detergentsalts. It is assumed'that the dye used does not change color with pI-Iand that when the lino representing its concentration crosses theminimum effective cleaning-concentration, that is, 0.5 per cent, itscolor rst becomes definitely detectible, as would vbe thezcase if such adye were to bc employed in a detergentto indicate optimum concentrationsof detergent. The color intensities are indicated on the axis at theright side of the gure and are expressed in arbitrary units. It isassumed that color perception occurs at a dye concentration of 1.5 ofthese units. The line representing the color intensities of a simple dyethus is a straight line starting at zero and passing through `the pointrepresenting a 0.5 per cent.

concentration of detergent-'and a color intensity of 1.5 units. Thelower dotted section of the line indicates the region in which a coloreddyc is present, itscolor being imperceptible in practice owing to itslow concentration.

Thecurve marked Color Intensity, Indicator A isdravvn upon theassumptionzthat a dye is employed which starts .to cha-nge in color at apH ofI about 8.6. The minimum effective concentration of detergentisassumed as before to be 0.5 per cent by'weight at which. point the pHof the solution, as read from the pH curve, is about 8.7. In otherwords, using this indicator, the quantity of indicator which should beadded to the detergent salts is that required to produce a detectablecolor when the pH reaches a Value of 8.7, corresponding to a detergentconcentration `of 0.5 per cent. .The curve representing colorintensityobviouslystartsat a concentration corresponding to a pHof about-8.6, atwhich the detergent concentration is about 0.35 per cent. The curve alsomust pass through the point of color perception (1.5 color intensityunits) and at a concentration of 0.5 per cent detergent. Thecolorintensity curve for the indicatorin question rises rapidly at thestart, eventually becoming substantially parallel to the color intensitycurve for the simple dye as the change in pH upon the additionofdetergent approaches zero. Here againthe lower section of the curverepresents the condition wherein a color is actually present butpractically imperceptible owing to lack of dye concentration. It will benoted, however, that this color intensity curve crosses the axisrepresenting zero color intensity at a point corresponding to aconcentration of detergent of about 0.35perrcent, i. e. a pH of 8.5. Itis .obvious therefore that, if a detergent concentration of 0.5 ypercent is operative, a concentration.of 0.35 per cent wouldbesubstantiallyequally effective, the differencebeing Very small.

Itis thus evident that no harm would result in adding aconsiderablefexcess of this particular indicator A tothe dry detergentsince, even ii its color became detectible at a pI-l' of 8.6-the extremelower end ofthe .coloi` range-a rather satisfactory .detergent solutionwould be produced at this pH. This. shows that, the closer the lower endofthe color-range of the indicator to the pH corresponding to theoptimum cleaning concentration of the detergent, the less the accuracyrequired in -adding the indicator to the detergent. Of course, foreconomy reasons, it is desirable to add only enough indicator to producea definite color perception at a point corresponding to the optimumcleaning concentration. But the increased flexibility obtained and thelower accuracy required, from the use of an indi cator whose changepoint is close to the optimum pH of the cleaner, are highly important.It is evident, of course, that it would be possible and mostadvantageous to employ an indicator the lower end of whose color rangecoincided with the pH of the optimum cleaning concentration, pro videdthat such an indicator should be available.

The curve marked Color Intensity, Indicator B in the drawing representsthe results obtained using an indicator the lower end of whose colorrange lies at a pH of about 8.1. This curve also passes through thecolor perception point at 1.5 color intensity units and a concentrationof 0.5 per cent. It lwill be noted immediately that this indicator isnot as effective as indicator A in designating optimum cleaningconcentrations. Thus, indicator A produces a color intensity of about3.2 units as the concentration changes from 0.5 to 1 per cent, while theindicator B gives a similar color intensity change of only 2.4 units.This compares with a color intensity change for the simple dye of 1.6units. Indicator A is about twice as eiectiv-e as the simple dye whileindicator B is about half again as eiective.

It is evident from the above that the usefulness of an indicator rapidlyfalls o as the lower end of its dominant color range approaches a pH of7. In fact it is evident from the drawing that an indicator the lowerend of whose color range approaches 7 would have no advantages over asimple dye in indicating optimum cleaning concentrations. Practicallyspeaking, an indicator the lower end of whose color range is below 7.2is not advantageous in the present invention.

My tests with indicators conirm the conclusions drawn from the curves ofthe drawing. A simple test can be made to determine what proportion ofthe color change produced by a given indicator in one of my detergentcompositions is due to pH change. In this test three quart bottles arefilled with water and to each is added a suflicient amount of indicatorto produce a perceptible color when the detergent (free from indicator)is added thereto in optimum cleaning concentration, say l teaspoonful,the amount of indicator added to each bottle being the same. Then to oneof the bottles a teaspoonful of detergent (free from indicator) isadded, to the second one-half teaspoonful and to the third one-fourthteaspoonful. If there is a denite color difference between bottles 1 and3 or l and 2, it follows that the indicator in question is suitable foruse in my invention, since it produced a change in color which is morethan that produced by-mere change in concentration of indicator. In thesame test three other quart bottles can be filled with water and tothese bottles may be added l, 1/2. A spoonful, respectively, of the samedetergent with indicator admixed. It will, of course, be noted that thecolor differences in this second series of bottles is much more markedthan in the rst set since, to the color change produced by change in pH,there is added the color change due to concentration of the indicator.

If phenolphthalein is used in the above test, having a color range orend point ending at about 8.1-8.3, it will be noted that in the rstseries of` bottles the color difference between bottles 1 and 3 will berather small, showing that the end point this indicator, correspondingapproximately to Indicator B of the drawing, falls close to the lowerend of the useful cleaning range. The second series of bottles will showdenite color differences due, of course, primarily to the concentrationeffect. In comparison, the indicator phthalein red shows a deiinitecolor diierence between all the bottles of the first series and an evengreater diierence between the bottles of the second series, the latterbeing the sum of the color differences due to pH and to dyeconcentration.

The curves in the drawing do not tell the complete story for the reasonthat it is recognized that the maximum rate of detectible color increasen a pH indicator lies on the side of its lower or less dominant color,and usually close to the end of its color range. I have found that it isnot practical to employ an indicator whose color disappears or becomesless dominant at the optimum pH of the detergent when approached fromthe low side. It follows that for best results the pH produced at theoptimum cleaning concentration of the cleaner should lie not only withinthe color range of the indicator but also between thehalf-transformation point and the lower end of the color range of theindicator. It is also evident that the curves of the drawing do not tellthe complete story for the reason that the indicators thymol blue andmeta cresol purple when subjected to the above tests, seem to produce atleast as good results as phenolphthalein in spite of the fact that thelower ends of their color ranges are usually stated as lying at a pH of8.6 and 7.6, respectively. A possible explanation for this may be thatthe col-or changes produced in the latter indicators, due to pH, may begreater than in the case of phenolphthalein through the range of optimumcleaning concentrations. That is, the bulk of the color change in thecase of phenolphthalein may occur close to its lower end point. Theprimary requirement is that the indicator produce an appreciable colorchange due to pH within the optimum cleaning concentration rang-e of thedetergent.

It is possible with the aid of the facts brought out above to formulaterather denite specifications for the indicators which are useful in thisinvention. These indicators must change in color or intensity, that is,give a color change throughout the pH range corresponding to the optimumcleaning concentrations of the detergent. This color change must be achange oi the dominant color of the indicator and this change mustterminate at its lower end at a pH ranging from about 7.2 to the pHcorresonding to the optimum cleaning concentration of the detergent. Andfor best results the indicator should be one whose half transformationpoint lies at or above the pH corresponding to the optimum cleaningconcentration of the indicator.

I have further found it advantageous to incorporate at least some soap,that is, an alkali metal salt of a high molecular fatty acid, in mydetergent composition. The soap produces a slightly milky or opalescenteffect which tends to enhance the color produced by the indicator. Itfurnishes a white background, so to speak, against which the color maybe viewed, even' when the solution is made up in a pail, for example.The quantity of soap added for this purpose should be at least about 25per cent vby weight of the detergent.

My invention also includes a method of making the :described detergentcompositions. I have found that the :best .wayqoi -adding .colorindicators .to a;detergent.composition isby spraying anvaqueousorfalcoholicosolution oflthe indicator on a 'mass Otdetergentlwhile .theymass is being agitated. When .the.indicatorrsolution dries thedetergent particleszare .thenvuniforimly coated with the dried=residuesof `the solution and segregation is avoided. If the detergentis notthoroughly dry it will ;,become .imoist rand somewhat sticky. duringthis:operation. And;the indicator usually changes ,to-its colorzinalkaline solution, that is, phenolphthalein, for example, produces apink color. Thissame `colorchange will occur if the detergent isdehydrated prior to the mixing,T operation :provided that it isheatedltoo strongly duringthei mixing. I have found that compositions.;made up in-these ways tend to change'ln color upon. standinginarelatively dry atmosphere; producinga iinalacolor corresponding to theneutralcolor of the indicator. That is, a detergent containingphenolphthalein will eventually become v.almost `colorless, adetergentfcontaining phthalein red will become yellow, a detergentcontaining thymol blue will become adightyellowto orange-color and adetergent `containing .meta cresol purple will vbecome a light browncolor. The :stable colors of these detergentsapparently.correspond totheneutral colors of the indicators.

t is, oi4 coursegdisadvantageous to haven` detei-gent change in colorduring storage and I have. found a method of avoiding'this difficulty.In this method the v,detergent is dehydrated at least partly beiorethemixing of the color.in dicator is completed. Preferably the detergent isthoroughly dehydrated before the mixing operation. The mixing operationis then conducted at a temperature ranging from about to 60 C.,thetemperature.employed depending upon theindicator but being so chosenthat the indicator does .not change substantially in color upon contactwith the detergent. When meta cresol'purpleis employed the dehydrateddetergent should be kept atiroom temperature or below during the mixing.operationtwhile with phthalein red the temperature may approach 60 C.It is advisable to use .alrather concentrated solution of the indicatorso that not too much solvent will be added to the detergent. Furtherdehydration after the addition of the indicator can thus be avoided.:This method produces a stable color.at once=which color .will notchange unless the detergent is hygroscopic.

It is usually advantageous to employ a compatible wetting agent inmy-.cleaning ccmpositions. This wetting agent can `be -made to lperforma double function, that is, awettingfagent can Abe employed 4which willserve as a .vehicle for the pH indicator as well as a .wettingagent perse. A large number of wetting agents are available which are of oilycharacter and'which readily dissolve pH indicators. These wetting agentscan be distributed .over the'surfacesof the cleaner particles andtendtoprevent'caking. They also prevent directcontactof theindicator with thealkaline salts .of .the cleaner, which'may be important if the indicatorisnothighly-stable towards alkalis. Among the wetting agents which aresuitable for'use withfmostalkaline detergent compositions, there may bementioned triethanol amine, pine oil, secondary alcohol sulates, such asTergitol 4 or .'l'iergitolx'lfpolymerized sodium salts of alkylatednaphthalene sulionic acids, monoethylphenol .sodum-rmonosulfonate,vsulfonated :castor `oil,su1fonated cresylicbase compound and sulfonated`cetyl alcohol.

It is usually advantageous to dissolve or disperse. the pH indicator inthe wetting agent before mixing -theztwo with the detergentsalts. If the.wetting agent is a solid, it can be melted or .preferably an inertsolvent-is used to maken solution of indicator vand wetting` agent. Inthe nal mixing operation, wherein the solution ordispersionofthelindicator in the wetting agent i: mixed-With thedetergent salts, it is desirable to spray the.y solution or dispersionover the salts whilethe latter arebeing agitated. This procedure evenlydistributes both wetting agent and indicator throughout the mass. Theindicatorwettingagent combination forms a lm coating on'the salts andhelps to prevent caking, for example. Any of `the usual Iorganicsolvents which are inerttowards Athe wetting agentand the indicator canbe used, such as alcohols. ketones or ethers. Usually either ethyl orpropyl alcohol will be found suitable.

Both thepI-I indicators and the wetting agents can be utilizedv in mycompositions in small proportions. The wetting agent can bey used inproportions ranging from about 0.2 to 10 per cent by weight while theconcentration of the indicator may range from about 0.004 to 0.02.percent, depending upon the indicator. With some indicators it is possibleto employ upto 1 per cent by weight. For .reasons 4of economy it ispreferred to employ the minimum concentrations of indicator which arecompatible with .the desired results and these concentrations usuallyrange from about 0.004 to 0.01 per cent.

Myinvention may be illustrated by reference to the following specificexamples which represent practical operating embodiments thereof.

Example 1 A composition was compounded containing the following:

Parts Sodium soap 75 Sodium metaborate tetrahydrate 12.5 Tetraesodiumpyrophosphate (10H20) 12.5

This mixture was ldehydrated by heating to about 60C. while stirring andthen cooled to approximately room temperature. An aqueoussolution'ofphenolphthalein (about 0.04 per cent by weight) wasthen'sprayed on the mixture while stirring and spraying was continueduntil a teaspoonful of the mixture, when added to a quart of water,produced a detectible pink color. The water in the phenolphthaleinsolution was rapidly absorbed by the detergent, the latter retaining itsdry pulverulent consistency. The color of the mixture was only slightlyoff white and this color Wasfound to be stable uponstanding. From theconcentration of the phenolphthalein solution and the quantity added itwas estimated that 0.004 per oentphenolphthalein on the dry basishad'been added.

Example 2 A. composition was compounded containing the following:

Parts Sodium soap 50 Sodium ,carbonate (10H20) 15 Di-sodium phosphate(12H20) 15 Sodium metasilicatepentahydrate 20 This-icompositionwasdehydrated and then an alcoholic solution of thymol bluewasaddeddropwise while stirring, the composition being slightly aboveroom temperature. This was continued until the detergent produced alight blue color when added to water in the amount of one spoonful to aquart. The thymol blue added amounted to 0.01 per cent on the dry basis.The nal composition was a light yellow color.

Example 3 The composition of Example 2 was dehydrated as before and thencooled to a temperature of about 15 C. when an alcoholic solution ofmeta cresol purple was sprayed on while stirring. This solution had beenacidied slightly by the addition of acetic acid to produce a yellowishbrown color. The addition of meta cresol purple was continued until thecomposition, when added to water in the amount of 1 teaspoonful to 1quart, produced a light purple color. This required a total of 0.008 percent on the dry basis. The color oi the resulting mixture was a lightbrown which faded only slightly upon standing.

It was found that, if the detergent salts were heated to a temperatureof about 70 C. during mixing, a light blue to lavender color resulted,which color faded to a light brown upon standing.

Example 4 A composition was compounded containing the followingcomponents:

To the above mixture, after dehydration, an alcoholic solution ofphthalein red was added while stirring until a light pink color wasproduced upon adding 1 teaspoonful of the mixture to 1 quart of water,the quantity added being about 0.014 per cent on the dry basis. Themixture was maintained at a temperature of about 40 C. during the mixingand the resulting color was found to be yellow. If slightly overheatedthis mixture produces a pink composition whose color gradually changesto yellow on standing. A concentration of phthalein red ranging fromabout 0.007 to 0.015 per cent is satisfactory for producing otherdetergent compositions within this invention.

Example 5 The composition of Example 1 was dehydrated and to this wasadded an alcoholic solution of a l Example 6 Parts Tetra-sodiumpyrophosphate (10H20) 78 Sodium carbonate (10H20) 26% Pine oil 3 Nileblue 1/ This indicator when added to tap water of about average hardnessin the amount of about 1 teal 0 spoonful to the gallon produces areddish mauve to rose color, a concentration which will be foundsuitable for most work, at lower concentrations a blue color isproduced.

Example 7 Parts Trisodium phosphate (12H20) 60 Sodium sesquisilicate(11H20) 27 Daxad l1 21/2 m-Nitro phenol 1,/2

This composition when added to water produces a faint yellow color whenthe concentration is about right for light cleaning and a bright yellowwhen it is suitable for heavier work.

Example 8 Parts Soap powder 20 Sodium metasilicate ennahydrate 43 Sodiummetaborate tetrahydrate 30 Beaconol A 5 Thymol blue 0.02

This composition makes a useful household cleaner and produces a yellowcolor at concentrations too low to be effective, a green color over arange suitable for light work and a bluish green to blue color atconcentrations suitable for ordinary work.

While I have described what I yconsider to be the most advantageousembodiments of this invention it is evident that various modications canbe made in the specific compositions and mixing procedures set forthwithout departing from the purview of this invention. As pointed outpreviously the alkaline detergent salts employed in my compositions canbe widely varied in nature and proportions depending upon the particularwork to be done. For some types of work a rather high proportion ofwetting agent is called for. But for ordinary purposes both the dye andwetting agent are employed in small amounts as compared with thedetergent salts. Any suitable mixing method may be employed to compoundmy compositions. It is always desirable to select alkaline salts for mycleaner which are stable and non-hydrogroscopic in spite of the factthat the wetting agent tends to prevent caking.

When wetting agents are employed in rather high proportions, it ispossible to tint the dry composition a color which corresponds to thatproduced upon dissolving the composition in water at the best cleaningconcentration. This is accomplished by treating the indicator with asmall amount of a slightly alkaline buffer solution of the desired pH,just prior to dissolving or dispersing it in the wetting agent. Afterthe mixture is coated on the cleaner particles, the color then remainsreasonably stable. It is more advantageous to buffer the wettingagent-indicator mixture to stabilize the color. One of the mostconvenient buffers to employ for this purpose is borax with a smallamount of boric acid or primary sodium phosphate added. But othercompatible buffers can be used. With cleaning preparations prepared inthis manner the user can be told merely to match the color of thecleaner in making the cleaning solutions.

In the case of most cleaning compositions it is possible to so selectthe color indicators that three colors are produced upon adding thecomposition to water in different proportions. In this case one colormay indicate when the concentration of the indicator is too low, anotherwhen it ls satisfactory for ordinary cleaning and the third color may beused asi av Warningthat the-concentration is-too high or at least sohigh that'thesolution should not be used onpaints,I for-example; Amixture of acyl red and thymol phthalein or 1,2,3-xylenol phthalein, forexample, is red up to a pH of about 9.5 when it begins to turn a mauvecolor and at a pH of vabout A10.5 itbecomes a'bluish green. Theindicator alkanin turnsfrozn red, through mauve to blue in the range of8.3*to and thus it alone forms a goodthree color; indicator. A mixtureofalpha naphtholA benzein and nitrothymol sulfonphthalein is violet up toa pH of about 9.2 when it begins` to turn a brownish color and then at apH of about 10.5 itturns green. It should be noted that, whenthree-color indicators are used as described, the pH is indicated notAonly by the color intensity but also by the shade of the color itself.This increases theaccuracy of this method. Other modifications of my.invention whichiallwithin thescope ofthe following claims will beimmediatelyv evident to those skilled in this art.

This is a continuation-in-part of my copending application, Serial No.569,625, led December 23, 1944, now abandoned.

What I claim is:

1. A detergent composition suitable for use in householdcleaning whichcomprises a mixture of nely-divided, solid, inorganic, alkalinedetergent salts which, when-dissolved in water in the concentrationrange of about 0.15 to 2 per cent by weight, produce cleaning solutionswhich have pI-Ifvalues Within the range ofabout 8.3 to 10.5

and producing pI-I'valuesnot` substantially ex- I ceeding 11 when addedto water in concentrations up to about 10 per cent by-weight, said`composition also containing at least abouti 25per centby weight of soapand from about 01.004 to0.02 per cent of a pH indicator havingtheproperty of changing in color due to -pI-I within said range of 8.3to 10.5 and-Whose end point occurs-at a pH substantially coinciding withthe pH corresponding to the lower end of the effective cleaning range of`said detergent composition, the quantity of indicator present beingcapableof producing a detectible coloration only upontheaddition ofsufcient detergent to water to produce approximately optimum cleaningconcentrations; said coloration then increasing in intensity uponiurther addition of the detergent due both to in'- crease in indicatorconcentration and to `change in pH.

2'. A detergent composition suitable for use in household cleaning whichcomprises a mixture of finely divided, solid, alkaline-reacting.`detergent salts capable ofbuffering solutions of said composition sothatthe pH values of said solutions do not substantially exceed 11`atconcentrations of up to about-10 percent by weight, said compositionforming cleaning solutions when added to water-in quantity producingconcentrations within the range of 0.15 to 2 per cent by weight withcorresponding pH' Values 1 within the range oi-about-B 4to 10.5, saidcomposition also containing from about' 0.004 -to 0.02 perifcent byweight of at least one pH' indicator:4 having? the property cf producinga1 characteristic change; in color within the range-ofpli-corresponding` to the optimum cleaning concentrations-of saiddetergent,- the'lower end-of the dominant color range of said-zindicato-rwsubstantially: coinciding with .the pH` corresponding to thelower end of the Veiective cleaning range of said composition, thequantity of pH. indicator presentbeingsuicentto produce a detectiblecoloration only: when sumcent detergent is dissolved-in water to give asolution within the cleaning range of frOm about 0.15 -to 2.0 vper centbyweight; said detergent upon gradual addition to Water initiallyproducing'- a detectible color withinsaid cleaning range, said colorthen increasing in intensity upon further addition of the detergent dueboth to increase in indicator concentration and to change in pH.

3. A dry nely-divided detergent composition comprisingapluralityofalkaline detergent salts producing-a buiering eiect upon aqueoussolutions and a pH within the range of about 8.3 to 9.7at-concentrations within the range of about 0.15 to 2 per cent by weightwith a maximum pH of not substantially above l1 at concentrations of uptoabout l0 per cent, said composition includingr at least about 25 percent of a soap and from about 0.007v to 0.015 per cent by weight ofphthalein redsulicient in amount to produce a detectible color onlywhensufficient detergent is dissolved in water to give a cleaning solutionwithin. the cleaning range of about 0.15A to 2.0.per cent by weight;said detergent upon gradual .addition to water initially producing adetectible color within said-cleaning range, said color thenincreasingin intensity upon further addition of the detergent due both to increasein indicator concentration and to change in pH.

4, A finely-divided, solid; householdv detergent composition comprisinga mixture of detergent saltswhich, when. dissolved in water at aconcentration ranging fromaboutl 0.15 to 2.0 per cent by weight,producesa cleaning solution having a pI-Iwithin'the range'of fromvabout'8.3 to 10.5"J the solid particles of said composition beinguniformly coated with-the dried, residues of a solution in a volatilesolvent ofa pH indicator capable of changing color1 withinY said pHrange, the lower end 4of the. color range otsaid indicator occurring ata., pH substantially coinciding with that ofthe lower end of.theeiective cleaning range of thecompcsition, the quantity of pI-Iindicator present in the composition being within the range of fromabout 0.004 to` 0.02per cent by weight and sumcient .to produce adetectible coloration when said composition is dissolved in water togive a cleaning solution having aconcentration within said range.

5. The process of making a detergent composition the color of whosesolutions is sensitive to change of pH Which comprises dehydrating asolid detergent composition comprising a plurality of alkaline detergentsalts capable of buffering aqueous solutions of said detergent so thatat concentrations of from about 5 to 10` per cent the maximum pHproduced is not substantially above 11; the composition having theproperty, when dissolved in water in the amount of from about 0.15 to 2per cent by Weight, of producing cleaning solutions within'the pH rangeof from about 8.3 to 10.5; gradually adding to the said composition asolutionin a volatilefsolvent of apH indicator having the property ofchanging in color due to changein pH within the; pH range of 8.3tc:.l0.5; said indicator .being'added in quantity amounting to fromabout 0.004 to 0.02 per cent by weight on the dry basis; and whileagitating and maintaining the temperature below about 60 C., whereby acomposition is produced whose color isstable and corresponds'to'thenatural color of said indicator.

ELIZABETH WESTON PARKER.

(References on following page) 13 14 REFERENCES CITED Number Name DateThe following references are of record in the 213651215 Rhodes Dec- 191944 le 0f this patent: FOREIGN PA'IENTS UNITED STATES PATENTS 5 NumberCountry Date Number Name Date 488,648 Great Brltain July 11, 19381,721,809 Buchanan July 23, 1929 OTHER REFERENCES al'lvll g Modern pHand Chlorine Control, booklet of W. 178;735 Behrman NW .7 1939 lo A.Taylor and Company, Balt. 1943) 6th ed.,

- a es 40 and 48. 2,137,536 Avedikian Jan. 16, 1940 p g

1. A DETERGENT COMPOSITION SUITABLE FOR USE IN HOUSEHOLD CLEANING WHICHCOMPRISES A MIXTURE OF FINELY-DIVIDED, SOLID, INORGANIC, ALKALINEDETERGENT SALTS WHICH, WHEN DISSOLVED IN WATER IN THE CONCENTRATIONRANGE OF ABOUT 0.15 TO 2 PER CENT BY WEIGHT, PRODUCE CLEANING SOLUTIONSWHICH HAVE PH VALUES WITHIN THE RANGE OF ABOUT 8.3 TO 10.5 AND PRODUCINGPH VALUES NOT SUBSTANTIALLY EXCEEDING 11 WHEN ADDED TO WATER INCONCENTRATION UP TO ABOUT 10 PER CENT BY WEIGHT, SAID COMPOSITION ALSOCONTAINING AT LEAST ABOUT 25 PER CENT BY WEIGHT OF SOAP AND FROM ABOUT0.004 TO 0.02 PER CENT OF A PH INDICATOR HAVING THE PROPERTY OF CHANGINGIN COLOR DUE TO PH WITHIN SAID RANGE OF 8.3 TO 10.5 AND WHOSE END POINTOCCURS AT A PH SUBSTANTIALLY COINCIDING WITH THE PH CORRESPONDING TO THELOWER END OF THE EFFECTIVE CLEANING RANGE OF SAID DETERGENT COMPOSITION,THE QUANTITY OF INDICATOR PRESENT BEING CAPABLE OF PRODUCING ADETECTIBLE COLORATION ONLY UPON THE ADDITION OF SUFFICIENT DETERGENT TOWATER TO PRODUCE APPROXIMATELY OPTIMUM CLEANING CONCENTRATIONS, SAIDCOLORATION THEN INCREASING IN INTENSITY UPON FURTHER ADDITION OF THEDETERGENT DUE BOTH TO INCREASE IN INDICATOR CONCENTRATION AND TO CHANGEIN PH.